The publication of the CCPS (Center for Chemical Process Safety) book ‘Bow Ties in Risk Management: A Concept Book for Process Safety’, is a nice opportunity to ask CGE’s program director about his thoughts on the book. CGE has been at the forefront of bowtie software since 2004, active as market leader in barrier-based risk management software across multiple industries. Below you will find the interview with Arjan Verboom.

What do you think of the CCPS book in general?

As CGE, we are really happy with the CCPS book coming out. Of course, we are firm believers in the value of the bowtie method and barrier management in general, so a comprehensive work that brings it all together is a great initiative and very welcome. I think the process safety industry will benefit from having a guideline to work from. It will help practitioners and future practitioners to build better bowtie diagrams and improve their analyses. Ultimately we believe this will make a contribution to a better understanding of risks and hopefully a safer working environment, not only in the chemical industry but in all major hazard industries.

Are the CCPS guidelines in line with how CGE teaches the bowtie methodology?

Yes, most definitely. We have contributed to the content in the book and are acknowledged as authors by the CCPS. Being involved in this way, there are no surprises, and the concepts we have been training our clients and partners in for years, are reflected in the content of the book. In addition to covering the basic bowtie concepts, the book discusses best practices for the bowtie development process, barrier management strategies and how to address human factors in the bowtie analysis. I think it’s really important that those topics have been written down in a book, as many companies find it challenging to take the next steps after making a decision to start analyzing their risks with bowties.

Given that CGE co-authored the book, one would assume that it is possible to follow the book’s guidelines in your software tool BowTieXP. Is that true?

That is indeed true. Our software allows doing bowtie analysis by following the guidelines in the book. Of the shelf, our software is already 99% in line with the book. The minor differences are in a few terms that we have used differently so far, such as ‘escalation factors’ instead of ‘degradation factors’. You can change the terminology with a single click, or customize our software completely to your own terminology and taxonomies. We offer a product that can be used in all industries, and different industries or companies use slightly different terms, that’s why our software offers customization.

How do you see the human factor approach in the bowtie model that CCPS advocates?

I suppose you mean how human factors, or human error, can be taken into account when formulating threats, barriers and degradation factors. In short, CCPS recommends to not include human error as a threat in the bowtie model, but to include them as degradation factors that could lead to the impairment of a main pathway barrier. In technical processes, that are mostly driven by hardware, this is a good approach. Therefore, given the main audience of the book, this is probably good advice.

However, for some industries, we see no harm in including specified human error scenarios as threats. The distinction should be if the human is part of a safety (barrier) system, or part of (or even driving) the main process and errs while executing the main business process. When the latter applies, a human error could very well be worded as a threat. This would be the same as if primary equipment breaks down, which is also commonly included as a threat. Industries, where this applies to, would be healthcare, construction and several activities in other industries. An example would be a crane operator moving a load by manually handling the controls. An excessive movement of the control stick, or a premature pushing of the release load button, could cause a loss of control moment.

As a solution to include human factors in bowties, CCPS advises to use them as degradation factors on a barrier and work out the controls in the same diagram. In addition, they offer an option to create multi-level bowties, where bowties are linked vertically. Modeling like this, the failure of a barrier in one bowtie could be subject to an in-depth analysis in a more granular chained bowtie. In that second level bowtie, the barrier failure becomes the top event and the failure mode becomes a threat (i.e. cause).

Our software supports multi-level bowties as proposed by CCPS as an advanced way of modeling and exploring human factors. BowTieXP supports the horizontal and vertical chaining of bowties. This and other advanced bowtie techniques that CCPS proposes are, without exception, available in BowTieXP.

In conclusion, there are multiple ways to apply the bowtie method. The chosen approach depends on the industry, the purpose of the bowtie and the level of detail you require or wish. However, we must not forget that the bowtie method is developed to make risks understandable. It is not an academic exercise, so we should be practical in our approach to reach the ultimate goal: work safer by understanding risk scenarios and managing barriers.

Thank you very much for this detailed answer. Is there anything else you would like to add that we haven’t talked about so far?

I realize that some readers might not be familiar with the method and therefore would have a bit of trouble following the last bit. This, however, is a good opportunity to urge them to go get the book, read it, and form their own opinions on the topics. There are very interesting topics to explore and the book gives really practical advice as well. I would say, a must read for all professionals in major hazard industries! The book is available at several online shops, including Wiley, Amazon and Bol.

Join the CCPS ‘Bow Ties in Risk Management’ webinar

With the concept book being released, we very much like to show you how to actually follow the book guidelines in our software tool BowTieXP. Join our webinar on to learn more about the CCPS guidelines on ‘Bow Ties in Risk Management’ and how it can be applied in practice with BowTieXP. These webinars will take place at:

We will close off with a live Q&A session, so you can ask us any questions you might have about the topic.

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